Limitations of 3D software.

Render Time.

Often, 3D animations, especially feature films can take a really long time to render. Avatar, for example took 2 days to render a single frame because of all the lighting and special effects added in. This is a limitation to working in 3D software because if you spend 2 days rendering out one frame, if a mistake has happened or something isn't right in the rendered frames, it could take weeks or months to correct the mistake and get back to where you started. This particularly affects the animation when working towards a strict deadline. 

Limitations.

A lot of 3D software is very expensive which makes it less easily accessible for people to use who don't animate at a company or place of education. The prices of the software mean that small non-funded or low- budget 3D animations aren't as commonly found as 2D traditional animation as software for that is a lot more accessible. Some 3D software can cost upwards of £3000 which, for a beginner, would be a lot of money to spend on the software to potentially not use again. 

Using 3D software for stop motion.

Thanks to 3D software, stop motion animation techniques have improved in leaps and bounds. 3D printing has enabled companies like Laika to create interchangeable faces for their characters, making lip syncing a much easier and faster process and it means that its easy to replace them if they break. For each full length film, Laika can produce up to 50000 faces overall. The ability to print whole faces off also means that every face for each character is identical and there wont be any unwanted small differences between frames, leading to a consistent animation.

Benefits of 3D over 2D animation.

The ability to animate in 3D has had a great impact on the animation world.
3D technology has meant that more realistic animations can happen and it's making it quicker to churn out lengthy animations because you don't need to draw every single frame. Once the characters and the set are modelled, key framing makes 3D animation a quick and effective animation style. 3D animation software also allows for effective camera angles and lighting effects that would be more challenging in 2D traditional animation. 

Computer Generated Imagery is being used a lot more often in modern film. It is used in live action films and fully animated features.

With 2D, everything is drawn out individually, but if an arm goes behind the character, you don't need to draw the arm. However with 3D, you need to be aware of every body part and its positioning even when they are obscured behind the figure. 
2D is obviously drawn on every frame and therefore takes a long time to sketch out, draw and colour each frame and you need to make sure each image is consistent and that the character doesnt change it's appearance between frames. This can be a challenge as tiny differences between frames arent noticeable straight away but become apparent over time while watching the animation through. 3D doesn't have this issue as the character will stay consistent between frames as you are just manipulating a modelled character.

Motion Capture.

Motion capture has improved film drastically. Using motion capture, it is possible to track an actors movements and gestures and apply them directly to a 3D model. This makes the characters movements more life-like and realistic. It works particularly well when the character being animated is within a scene or interacting with actors in a live action motion picture, for example, if a character is a mythological creature like a troll or an ogre and the entire character is needed to be created digitally.

It also makes the animation process a lot faster as each position is not having to be key framed by hand individually.